#include <bits/stdc++.h>
#include "dna.h"
using namespace std;
const int N = 1e5+7;
int cnt[3][3][N], cnta[3][N], cntb[3][N];
int id[256];
void init(std::string a, std::string b) {
id['A'] = 0;
id['C'] = 1;
id['T'] = 2;
const int n = a.size();
for (int i = 0; i < n; ++i) {
const int x = id[(int)a[i]], y = id[(int)b[i]];
for (int p = 0; p < 3; ++p) {
cnta[p][i+1] = cnta[p][i];
cntb[p][i+1] = cntb[p][i];
for (int q = 0; q < 3; ++q) cnt[p][q][i+1] = cnt[p][q][i];
}
cnt[x][y][i+1]++;
cnta[x][i+1]++;
cntb[y][i+1]++;
}
}
int get_distance(int x, int y) {
++y; // [x, y)
for (int i = 0; i < 3; ++i) {
if (cnta[i][y] - cnta[i][x] != cntb[i][y] - cntb[i][x]) return -1;
}
vector q(3, vector<int>(3));
for (int i = 0; i < 3; ++i)
for (int j = 0; j < 3; ++j) {
q[i][j] = cnt[i][j][y] - cnt[i][j][x];
if (i == j) q[i][j] = 0;
}
int ans = 0;
for (int s = 0; s < 3; ++s)
for (int t = 0; t < s; ++t) {
int delta = min(q[s][t], q[t][s]);
ans += delta;
q[s][t] -= delta;
q[t][s] -= delta;
}
int lam = 0;
for (auto& u : q) for (int x : u) lam += x;
ans += lam / 3 * 2;
return ans;
}
